Telephone-exchange system



F. V. YOUNG.

TELEPHONE EXCHANGE SYSTEM.-

APPLICATION FILED OCT. 2. 19H.

1 ,325, 1 84 Patented Dec. 16, 1919.

76 Opens I'e/.

knew/0r. Frederick [K Young by M . AV/j UNITED STATES PATENT OFFICE.

FREDERICK V. YOUNG, F CHATHAM, JERSEY, ASSIG-NOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y. A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Dec. 16, 1919.

Application filed October 2, 1917. Serial No. 194,308.

To all whom it may concern:

Be it known that I, FREDERICK V. YoUNc, a citizen of the United States, residing at Chatham, in the county of Morris and State of New Jersey, have invented certaln new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact descrlptlon.

This invention relates to telephone exchange systems and more particularly to trunk circuits employed in connecting together telephone lines terminating at (llfiGT- ent switchboards.

It is an object of this invention to provide a simple two-way trunk or transfer circuit which employs only two conductors and a minimum amount of apparatus so connected with and controlled over the trunk circuit as not to impair the transmission efiiciency of the circuit.

In accordance with this invention, there is provided a trunk or transfer circuit of two conductors extending between and term nating in switching terminals at two swltchboards and having at each end a relay bridged from one conductor to ground, which'coiiperates with the switching terminals thereat to control the corresponding signaling device. 7

For a more complete understanding of this invention, reference should be had to the following description considered in connection with the accompanying drawing containing one embodiment of this invention.

Referring to the drawing, there is shown a trunk circuit B extending from a switchboard X at which is located a cord circuit C to a switchboard Y at which is located a cord circuit D. These two cord circuits are exactly alike and only so much of the apparatus of each cord circuit as pertains to this invention is shown in the drawing. The trunk circuit B composed of two conductors 5 and 6 terminates at the switchboard X in a jack 7 and at the switchboard Y in a jack 8. A condenser 9, located at the switchboard X, is connected in the trunk conductor 5 and a similar condenser 10 located at the switchboard Y is similarly connected in the trunk conductor 6. A relay 11 is bridged from the trunk conductor 5 to ground, the point of connection with the conductor 5 being between the condenser 9 and the distant end of the trunk circuit. A

similar relay 12 located at the switchboard Y is bridged from thetrunk conductor 6 to ground, the point of connection with the conductor 6 being between the condenser 10 and the distant end of the trunk circuit. A lamp 13 located at the switchboard X and associated with the trunk circuit is controlled by contacts of the relay 11 and local contacts of the jack 7 A lamp 14 located at the switchboard Y is controlled by contacts of the relay 12 and local contacts of the jack 8.

Referring now to the operation of the system disclosed in the drawing, the operator at switchboard X desiring to extend a call to the switchboard Y, inserts plug of the cord circuit G into the jack 7 of the trunk circuit B, whereupon local jack contact 21 is opened and contact 22 is closed. The closure of contact 22 of the jack 7 causes the lighting of lamp 13 over a circuit from battery through contact 22 and the normal contact of relay 11 to ground. Upon the insertion of plug 20 into jack 7 relay 12 is operated over a circuit from battery through the left-hand winding of supervisory relay 23, ring contacts of the plug 20 and jack 7, conductor 6 and the winding of relay 12 to ground. Relay 12, in operating, causes the lighting of lamp 14 over a circuit from. battery through contact 25 of jack 8 and the alternate contact of relay 12 to ground.

The operator at switchboard Y, observing the lighted condition of lamp 14, inserts plug of the cord circuit D into the jack 8, whereupon contact 25 of the jack is opened and contact 26 closed. The opening of contact 25 opens the circuit through the lamp 14 extinguishing the lamp. The insertion of plug 30 into the jack 8 also causes the operation of relay 11 over the circuit from battery through a winding of supervisory relay 31, ring contacts of the plug 30 and jack 8, conductor 5 andwinding of relay 11 to ground. Relay 11, in operating, opens the circuit of'lamp 13, which is thereby extinguished. Immediately upon inserting the plug 30 into jack 8, the operator at switchboard Y actuates listening key 32 connecting the telephone set across the talking circuit, and the operator at switchboard X upon observing the extinguishment of the lamp 13 actuates listening key 33 to connect the telephone set to the talking circuit. The operator at switchboard X may now transmit to the operator at switchboard Y the number of the line desired. The operator at B may then complete the connection in any manner desired. At the conclusion of the conversation, the operators may withdraw the plugs from the jacks, restoring all apparatus to normal condition.

It is thought that from the above description it will be evident just how the apparatus functions it the call had originated at the switchboard Y instead of the switclr board X. A detailed description of setting up this connection will therefore not be necessary.

From the above description, it will be noted that this invention provides a simple two-way trunk circuit comprising only two conductors and requiring only two relays, one at each end, which cooperate with local jack contacts to control the operating circuits of the respective lamps located at each end of the trunk circuit. The relays are connected from the talking conductors to ground and should preferably be of high impedance so as not to impair the talking efficiency of the trunk circuit,

and the condensers, while preventing the passage of direct current, permit the passage of currents of telephonic frequency.

What is claimed is:

1. A telephone exchange system comprising a two-conductor trunk circuit extending between two switchboards and terminating at each in a jack, a condenser in each trunk conductor, one of the condensers being located at each switchboard, a cord circuit at one switchboard, a signaling device at the other switchboard, a relay thereat connected with one of the trunk conductors between the condenser thereof and the other switchboard and responsive to the connection of the cord circuit with the trunk eir cuit, and an operating circuit for the signal ing device including a contact of the relay and ack at said other switchboard.

2. A. telephone exchange system comprising a two-conductor trunk circuit extending from a first to a second switchboard, a con denser in each trunk conductor, one of the condensers being located at each switchboard, a cord circuit and a signaling device located at each switchboard, a relay at the first switchboard connected with one of the trunk conductors between the condenser thereof and the second switchboard and responsive to the connection of the cord cir-. cuit at the second switchboard with the trunk circuit, a relay at the second switchboard similarly connected with the other trunk conductor and similarly controlled from the first switchboard, and operating circuits "for the signaling devices closed when either cord circuit is connected with the trunk circuit and open when both cord circuits are connected with the trunk circuit.

3. A telephone exchange system comprising a two-conductor trunk circuit extending from a first to a second switchboard and terminating at each in jacks, a condenser in each trunk conductor, one of the condensers being located at each switchboard, a cord circuit and a signaling device located at each switchboard, a relay at each switchboard bridged to ground from the trunk conductor in which is connected the condenser, each relay being responsive to the connection of the cord circuit at the other switchboard with the trunk circuit, and operating" circuits for the signaling devices controlled by the relays and including contacts of the jacks.

a. A telephone exchange system comprising a two-conductor trunk circuit extending from a first to a second switchboard and terminating at each in a ack, a condenser in each trunk conductor, one of the condensers being located at each switchboard, a cord circuit and a signaling device located at each switchboard, a relay at each switchboard bridged to ground from the trunk conductor in which the condenser is connected, each relay being responsive to the connection of the cord circuit at the other switchboard with the trunk circuit, an operating circuit for each signaling device in eluding a normally closed contact of its associated jack and a normally open contact of its associated relay, and a second operating circuit for each signaling device including a normally closed contact of its associated relay and anormally open contact of its associated jack.

In witness whereof I hereunto subscribe my name this 27th day of September A. D.,

FREDERICK V. YOUNG. 

